1 / 10

OFDM(A) Competence Development – Part IV

OFDM(A) Competence Development – Part IV. Per Hjalmar Lehne, Frode Bøhagen , Telenor R&I R&I seminar, 23 January 2008, Fornebu, Norway Per-hjalmar.lehne@telenor.com Frode.bohagen@telenor.com. Outline. Part I: What is OFDM? Part II: Introducing multiple access: OFDMA, SC-FDMA

Download Presentation

OFDM(A) Competence Development – Part IV

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. OFDM(A) Competence Development – Part IV Per Hjalmar Lehne, Frode Bøhagen, Telenor R&I R&I seminar, 23 January 2008, Fornebu, Norway Per-hjalmar.lehne@telenor.com Frode.bohagen@telenor.com

  2. Outline • Part I: What is OFDM? • Part II: Introducing multiple access: OFDMA, SC-FDMA • Part III: Wireless standards based on OFDMA • Part IV: Radio planning of OFDMA OFDM Competence Development

  3. OFDMA Radio Planning • No difference in the principal planning procedure compared to GSM and UMTS • Steps in a planning procedure: • Find the input parameters • Define cell edge quality • Calculate coverage • Calculate capacity • Input parameters: • power • frequency reuse scheme • etc… Define edge quality If coverage or capacity do not meet requirements Coverage • Results: • Path loss • Cell range • Results: • Cell capacity • Throughput distributions Capacity Subcarrier orthogonality => OFDMA planning has more resemblance with GSM planning than UMTS planning Done OFDM Competence Development

  4. Frequency Reuse • Frequency reuse is a source to co-channel-interference (CCI) • Traditional GSM planning uses relatively large FRF (Example: FRF = 7) • For new OFDMA systems smaller FRFs are suggested (typical FRFs of 1 or 3) Smaller FRF => Inter cell interference for OFDMA systems closer to UMTS than GSM OFDM Competence Development

  5. Reuse Factor = 1 • Referred to as universal frequency reuse • Reuse 1 => always highest spectral efficiency • Usually combined with interference randomization • Frequency hopping • Frequency domain scrambling OFDM Competence Development

  6. Reuse Factor = 3 • Increased spatial separation between co-channels • Eliminates CCI at the sector boundaries • Significantly decreases CCI between neighbour cells OFDM Competence Development

  7. f1 f2 f3 frequency Fractionally Frequency Reuse • Procedure • Users are designated into multiple classes (e.g. cell centre and cell edge) • Different frequency resources are assigned for different user classes • Transmissions across BSs and sectors are coordinated so that maximal interference avoidance is achieved f1+ f2+ f3 OFDM Competence Development

  8. DL subframe UL subframe Preamble Centre cell with FRF =1 Whole cell with FRF =3 Centre cell with FRF =1 Whole cell with FRF =3 Fractionally Frequency Reuse • Time coordination • Power coordination • Result: Frequency reuse factor between 1 and 3 OFDM Competence Development

  9. Link budget • Studying OFDMA link budgets reveals • No big surprises • Interference margins between 1-6 dB suggested • Example: E-UTRA link budget (outdoor) OFDM Competence Development

  10. Summary: OFDMA radio planning • No principal difference in radio planning for OFDMA compared to existing systems (WCDMA/TDMA/FDMA) • Interference properties of OFDMA • Limited inter-cell-interference due to orthogonal subcarriers (similar to GSM) • Large intra-cell-interference due to small FRF (similar to UMTS) • Interference margins suggested 1 - 6 dB • Fractionally frequency reuse suggested to trade off fairness with efficiency OFDM Competence Development

More Related